1. Field of the Invention
This invention relates to a television intercom system. More particularly, the invention relates to a television intercom system equipped with a picture bus controller for supplying respectively an electric power source to a camera-equipped entrance substation, a monitor master station and an expanded monitor master station.
2. Description of the Related Art
A television intercom system having a structure shown in FIG. 2 is known as the television intercom system of the kind described above. In the drawing, the conventional television intercom system includes a camera-equipped entrance substation 10 installed at a residential entrance, a monitor master station 20 and an expanded monitor master station 30 that are installed inside the residence, a picture bus controller 40 for respectively supplying electric power sources to the camera-equipped entrance substation 10, the monitor master station 20 and the expanded monitor master station 30, and an electric power source main adaptor 50 connected to the picture bus controller 40. The camera-equipped entrance substation 10 is connected to the picture bus controller 40 through a first connection line L10. The monitor master station 20 and the expanded monitor master station 30 are connected to the picture bus controller 40 through a second connection line L20, and the electric power source main adaptor 50 is connected to the picture bus controller 40 through a third connection line L30.
The camera-equipped entrance substation 10 includes a picture electric power source separation circuit 110 (hereinafter called “entrance picture electric power source separation circuit 110”), an electric power source circuit 120 (hereinafter called “entrance electric power source circuit 120”) and a camera circuit 130 (hereinafter called “entrance camera circuit 130”). The entrance picture electric power source separation circuit 110 is connected to the entrance electric power source circuit 120, the entrance camera circuit 130 and the first connection line L10.
The monitor master station 20 includes a picture electric power source separation circuit 210 (hereinafter called “master station picture electric power source separation circuit 210”), an electric power source circuit 220 (hereinafter called “master station electric power source circuit 220”) and a monitor circuit 230 (hereinafter called “master station monitor circuit 230”). The master station picture electric power source separation circuit 210 is connected to the master station power source circuit 220, the master station monitor circuit 230 and the second connection line L20.
The expanded monitor master station 30 includes a picture electric power source separation circuit 310 (hereinafter called “expanded master station picture electric power source separation circuit 310”), an electric power source circuit 320 (hereinafter called “expanded master station electric power source circuit 320”) and a monitor circuit 330 (hereinafter called “expanded monitor circuit 330”). The expanded master station picture electric power source separation circuit 310 is connected to the expanded master station electric power source circuit 320, the expanded monitor circuit 330 and the second connection line L20.
The picture bus controller 40 includes a monitor electric power source picture circuit 410, a picture signal amplifier circuit 420, a camera electric power source picture circuit 430 and an electric power source main circuit 440. The monitor electric power source picture circuit 410 is connected to the picture signal amplifier circuit 420, the second connection line L20 and the electric power source main circuit 440. The electric power source main circuit 440 is connected to the third connection line L30. The electric power source main circuit 440 is further connected to the picture signal amplifier circuit 420 and the camera electric power source picture circuit 430. The camera electric power source picture circuit 430 is connected to the picture signal amplifier circuit 420 and the first connection line L10.
Next, the operation of the television intercom system having such a structure will be explained. During stand-by, the electric power source main adaptor 50 supplies the electric power source to the electric power source main circuit 440. The electric power source is further supplied from this electric power source main circuit 440 to the entrance electric power source circuit 120 through the camera electric power source picture circuit 430, the first connection line L10 and the entrance picture electric power source separation circuit 110. At the same time, the electric power source is respectively supplied to the picture electric power source separation circuit 210 and to the expanded master station picture electric power source separation circuit 310 through the monitor electric power source picture circuit 410 and the second connection line L20. Also, the electric power source is respectively supplied from the master station picture electric power source separation circuit 210 to the master station electric power source circuit 220 and from the expanded master station picture electric power source separation circuit 310 to the expanded master station electric power source circuit 320. Consequently, the electric power source is already supplied to each part (circuit) with the exception of the camera circuit 130 of the camera-equipped entrance substation 10, the monitor circuit 230 of the monitor master station 20 and the monitor circuit 330 of the expanded monitor master station 30.
Here, when a visitor pushes a call button (not shown in the drawings) of the camera-equipped entrance substation 10 and calls the monitor master station 20, the operation power source is respectively supplied from the entrance electric power source circuit 120 to the camera circuit 130, from the master station electric power source circuit 220 to the master station monitor circuit 230 and from the expanded master station electric power source circuit 320 to the expanded monitor circuit 330.
When the camera circuit 130, the master station monitor circuit 220 and the expanded monitor circuit 330 become operative, a picture signal of the visitor picked up by a camera (not shown) constituting the camera circuit 130 of the camera-equipped entrance substation 10 is transferred to the master station picture electric power source separation circuit 210 and to the expanded master station picture electric power source separation circuit 310 through the entrance picture electric power source separation circuit 110, the first connection line L10, the camera electric power source picture circuit 430, the picture signal amplifier circuit 420, the monitor electric power source picture circuit 410 and the second connection line L20, and is respectively transferred from the master station picture electric power source separation circuit 210 to the master station monitor circuit 230 and from the expanded master station picture electric power source separation circuit 310 to the expanded monitor circuit 330. Consequently, the picture of the visitor is displayed on a monitor (not shown) constituting each of the master station monitor circuit 230 and the expanded monitor circuit 330.
In the television intercom system having the structure described above, however, the electric power source is supplied from the electric power source main circuit for operating the camera circuit 130, the master station monitor circuit 220 and the expanded monitor circuit 330. Therefore, when a television intercom system having an expanded monitor master station and a television intercom system not having such an expanded monitor master station are compared with each other, a greater capacity of the electric power source required for the electric power source main adaptor 50 is necessary in the former than in the latter. In other words, in the television intercom system having the expanded monitor master station, the electric power source main adaptor 50 must have a large power source of a separate kind so as to the expanded monitor master station that is added. It is also necessary to supply to the market an electric power source adaptor having a greater capacity than the electric power source main adaptor 50 to be used in the case where the expanded monitor master station is not added. However, the cost of production drastically rises in this case.